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    <title>ShellCheck: SC3047 – In POSIX sh, trapping ERR is undefined.</title>
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    <h1>SC3047 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC3047">See this page on GitHub</a>
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    <h2 id="in-posix-sh-trapping-err-is-undefined">In POSIX sh, trapping ERR
is undefined.</h2>
<p>(or "In dash, ... is not supported." when using
<code>dash</code>)</p>
<p>Also applies to RETURN and DEBUG.</p>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC3047.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="co">#!/bin/sh</span></span>
<span id="cb1-2"><a href="SC3047.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="bu">trap</span> <span class="st">&#39;Command failed with $?&#39;</span> ERR</span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<p>Switch to a shell like <code>ksh</code> or <code>bash</code> that
<em>does</em> support the kind of trap you want:</p>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC3047.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="co">#!/bin/bash</span></span>
<span id="cb2-2"><a href="SC3047.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="bu">trap</span> <span class="st">&#39;Command failed with $?&#39;</span> ERR</span></code></pre></div>
<p>Otherwise, rewrite the script to not rely on the trap.</p>
<h3 id="rationale">Rationale:</h3>
<p>You are trying to install a trap that is not supported by your
current shell (<code>dash</code> or POSIX <code>sh</code>). There is no
simple replacement. The script should be rewritten to avoid depending on
the trap, or simply be run with a shell that supports it.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>If you only intend to target shells that supports this feature, you
can change the shebang to a shell that guarantees support, or <a
href="ignore.html">ignore</a> this warning.</p>
<p>You can use <code># shellcheck disable=SC3000-SC4000</code> to ignore
all such compatibility warnings.</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
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    <p style='font-size: 80%'><a href="../index.html">ShellCheck</a> is a static analysis tool for shell scripts. This page is part of its documentation.</p>
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